Wobble signal detection

Abstract

Wobble detection for detecting data in a wobble signal modulated with a base signal includes sampling the wobble signal at a substantial maximum and a substantial minimum of a base signal within a wobble period, producing a value of the wobble signal at the substantial maximum of the base signal with an unchanged sign and a value of the wobble signal at the substantial minimum of the base signal with a reversed sign, determining a sum of the values within the wobble period, and decoding the sum to detect data.

1. A wobble detection method for detecting data in a wobble signal, comprising:
 sampling the wobble signal at a substantial maximum and a substantial minimum of a base signal within a wobble period; 
 producing a value of the wobble signal at the substantial maximum of the base signal with an unchanged sign and producing a value of the wobble signal at the substantial minimum of the base signal with a reversed sign; 
 generating a sum of the values within the wobble period; and 
 decoding the sum to detect data. 
 
   
   
     2. The method as claimed in  claim 1 , further comprising comparing the sum to a threshold and determining a result to be used in decoding. 
   
   
     3. The method as claimed in  claim 2 , wherein comparing compares the sum to a positive threshold and a negative threshold. 
   
   
     4. The method as claimed in  claim 3 , wherein data are a first data type when the sum exceeds the positive threshold, data are a second data type when the sum exceeds a negative threshold and data are a third data type when the sum is between the positive and negative thresholds. 
   
   
     5. The method as claimed in  claim 4 , wherein the first data type is monotone wobble, the second data type is inverted wobble and the third data type is undefined. 
   
   
     6. The method as claimed in  claim 4 , wherein the first data type is one, the second data type is zero and the third data type is monotone wobble. 
   
   
     7. The method as claimed in  claim 4 , wherein the first data type is normal phase wobble, the second data type is inverted phase wobble and the third data type is undefined. 
   
   
     8. The method as claimed in  claim 1 , wherein the base signal is at a carrier frequency ω of the wobble signal. 
   
   
     9. The method as claimed in  claim 8 , wherein the base signal is cos(ωt). 
   
   
     10. The method as claimed in  claim 8 , wherein the base signal is sin(ωt). 
   
   
     11. The method as claimed in  claim 1 , wherein the base signal is at a harmonic of a carrier frequency ω of the wobble signal. 
   
   
     12. The method as claimed in  claim 11 , wherein the harmonic is the second harmonic. 
   
   
     13. The method as claimed in  claim 12 , wherein sampling includes sampling the wobble signal at substantially 0.125, 0.375, 0.625 and 0.875 of the cycle. 
   
   
     14. The method as claimed in  claim 1 , further comprising generating a sum for a plurality of wobble periods before decoding. 
   
   
     15. The method as claimed in  claim 1 , wherein sampling includes sampling at a plurality of maxima and a plurality of minima within the wobble period. 
   
   
     16. The method as claimed in  claim 15 , wherein the plurality equals two. 
   
   
     17. A detector for use with an optical pickup unit outputting a wobble signal, the detector comprising:
 a sampler to discretely sample the wobble signal at a substantial maximum and a substantial minimum of a base signal within a wobble period; 
 an alternate sign operator to change a sign at alternate samples and to output resultant values; 
 an accumulator to sum the values output by the alternate sign operator within the wobble period; and 
 a decoder to decode a sum output by the accumulator. 
 
   
   
     18. The detector as claimed in  claim 17 , further comprising a comparator to compare the sum output by the accumulator with a threshold and to output a result to the decoder. 
   
   
     19. The detector as claimed in  claim 18 , wherein the comparator compares the sum to a positive threshold and a negative threshold. 
   
   
     20. The detector as claimed in  claim 19 , wherein data are a first data type when the sum exceeds the positive threshold, data are a second data type when the sum exceeds a negative threshold and data are a third data type when the sum is between the positive and negative thresholds. 
   
   
     21. The detector as claimed in  claim 20 , wherein the first data type is monotone wobble, the second data type is inverted wobble and the third data type is undefined. 
   
   
     22. The detector as claimed in  claim 20 , wherein the first data type is one, the second data type is zero and the third data type is monotone wobble. 
   
   
     23. The detector as claimed in  claim 20 , wherein the first data type is normal phase wobble, the second data type is inverted phase wobble and the third data type is undefined. 
   
   
     24. An article of manufacture having a machine-accessible medium including data that, when accessed by a machine, cause the machine to detect data in a wobble signal, detection comprising:
 sampling the wobble signal at a substantial maximum and a substantial minimum of a base signal within a wobble period; 
 producing a value of the wobble signal at the substantial maximum of the base signal with an unchanged sign and producing a value of the wobble signal at the substantial minimum of the base signal with a reversed sign; 
 generating a sum of the values within the wobble period; and 
 decoding the sum to detect data.